Anti-jackknifing control system, apparatus and method

ABSTRACT

A system including an anti-jackknifing abutment apparatus (FIGS. 1-4, 7, 8) and electrical (FIG. 5) and hydraulic (FIG. 6) controls provides system control which controls limited relative angular movement between an articulated tractor 10 and trailer 20. An engagement driver in the form of cylinder 36 mounted within a rigid frame 23 is mounted by a mounting bar 25 to a forward beam member 22 of the trailer 20 for moving a abutment element 28, 128 into and out of an engagement zone within the longitudinal V-slot 17 of the fifth wheel 14. The abutment element in position on a rotational swing of the articulated vehicle is contacted by ears 18 of the V-slot, where due to the structure of the apparatus, the further rotational movement may be arrested or controlled to permit adjustment of the rotational limit of further angular movement under control of the driver. The system can be adjusted and controlled to permit adaption of the moving vehicle to various road and rig movement conditions, acting to prevent dangerous jackknifing from occurring.

RELATED APPLICATIONS

This application is a continuation in part of U.S. Ser. No. 06/758,677,now abandoned, filed July 7, 1985 entitled Anti-Jackknifing Apparatusfiled by the applicants, and now abandoned, in favor of the co-pendingNational Phase continuation-in part application U.S. Ser. No. 847,068filed Apr. 1, 1986, based upon PCT/US 01447 filed July 11, 1986 entitledAnti-Jackknifing Control System, Apparatus and Method and continuingapplication U.S. Ser. No. 06/922,439 filed Oct. 23, 1986 entitledAnti-Jackknifing Apparatus, and divisional application U.S. Ser. No.06/922,440 filed Oct. 23, 1986 also entitled Anti-Jackknifing Apparatus.

BACKGROUND OF THE INVENTION

The field of devices of the inventions are those designed for preventingjackknifing between a truck and trailer and the method of operation ofthe system.

Jackknifing has been ranked as the third most hazardous type of truckaccident, accounting in the United States of America for approximately$20,000,000 of property damage and more than 5% of the fataltruck-trailer accidents. Safe driving practices such as keeping speeddown to a safe speed for road conditions, avoidance of suddendecelerations and slippery surfaces or loose dirt, safe easy stops andsmooth steering substantially improve the risk of a jackknifeoccurrence. Nevertheless the jackknife accident continues to occurthousands of times a year.

Trucks pull a trailer through a fifth wheel-kingpin connection whichallows the tractor and trailer to pivot about the axis of thisconnection. The huge tractor rigs on the highway are guided by the smallfront tire footprint on the road. When braking, even at slow speeds, theinertia forces push at an angle against the pivot point connection andthe trailer swings around pulling the tractor out of position, breakingthe front tire contact, and causing a complete loss of control and a"jackknife" occurs as the trailer and tractor pivot on the kingpinconnection toward each other to close like a knife blade enters thehandle in a camper's jackknife. Uneven braking can trigger thephenomena, as well as side winds, sudden engine deceleration and loss ofbraking. The trailer can override the tractor pushing it into jackknifeor the tractor can underride the trailer and cause the jackknife. Thesevariable causes make a practical solution to the problem difficult.

This problem has long been known. It has been known for at least adecade that corrective action needs to be taken before the angle betweena tractor and trailer exceeds 15 degrees. Over the years many"solutions" to this problem have been suggested. In the last decadeelectrical brakes were suggested as a means to reduce the jackknifeoccurrence, and these were employed on many trailers. However, thissystem did not effectively work and few vehicles use this "solution".Since 1975 so called anti-lock systems known as 121 brakes required byU.S. Federal Motor Vehicle Safety Standard 121 have been employed toautomatically release brakes on an axle or tandem if any wheel locks upmore than momentarily. Still sudden brake applications can cause wheellock-up. Hand valves to cause trailer wheels to lock to preventjackknifes have been proposed, but the U.S. National Safety Councilfound this solution could actually induce trailer jackknifes. Driverswho over-accelerate in a effort to pull out of such an induced jackknifemay induce a tractor jackknife by spin-out.

While there are only six fundamental machines the field of mechanismsand structures may be unlimited. However, in this art here have beennumerous suggestions in prior art attempts. An effective solution needsto be cost effective and safe and reliable. The many prior art devicessuggested by the patent literature are not seen on the vehicles on theroad today and jackknife accidents continue to occur. If an effectivesolution had been achieved, in view of the clear need, one of the priorart devices should have been adopted widely prior to this time. Withsuch a number of prior devices available, without the use of hindsight,a description of relevant background prior art applicable to the presentinvention would not be readily apparent. In the prior art there doesexist many attempts to limit the amount of pivotal movement of the fifthwheel and kingpin of a tractor-semitrailer combination and other variousarrangements to prevent or minimize the tendencies of tractor-trailersto jackknife. However, these arrangements do not provide apparatus whichare adjustable to road conditions as does the present apparatus and theydo not provide a control system for continuous monitoring of ananti-jackknifing apparatus which limits swing to a anti-jackknifingcontrolling arc and which allow the driver to control the vehicle andcontrol apparatus in accordance with varying road conditions and rigmovement and which has the other features which will be described. Arepresentative sample of the prior art granted over many years may belisted as follows:

U.S. Pat. No. 2,462,211, filed Feb. 24, 1947 to C. L. Moore

U.S. Pat. No. 2,553,959, issued May 22, 1951 to H. F. Cook et al.

U.S. Pat. No. 2,652,262, filed Oct. 19, 1950 to W. G. Sherry

U.S. Pat. No. 2,962,301, filed Oct. 15, 1959 and issued November, 1960to W. J. Leinbach

W. Ger. Pat. No. 960,696 issued Mar. 7, 1957 naming Hans Becker asinventor

U.S. Pat. No. 3,031,205, issued Apr. 24, 1962 to P. Fox

U.S. Pat. No. 3,063,739, issued Nov. 13, 1962 to P. M. Davies

U.S. Pat. No. 3,420,548, filed Oct. 7, 1966 to C. M Wakeman

U.S. Pat. No. 3,588,809, issued June 28, 1971 to A. S. Devlin

U.S. Pat. No. 3,774,941, filed Feb. 14, 1972 to H. H. Durr

U.S. Pat. No. 3,837,678, filed May 3, 1973 and issued September, 1974 toR. Cicero

U.S. Pat. No. 3,856,329, issued Dec. 24, 1974 to M. A. Ordorica

U.S. Pat. No. 3,895,827, issued July 22, 1975 to J. D. Padrick

U.S. Pat. No. 3,972,542, issued Aug. 3, 1976 to Arthur A. Dirks

U.S. Pat. No. 4,040,006, issued Aug. 2, 1977 to R. W. Kimmel

U.S. Pat. No. 4,068,860, issued Jan. 17, 1978 to A. Dirks and W. Meyers

U.S. Pat. No. 4,556,232 issued Dec. 3, 1985 to J. I. Sever

Such a hindsight collection of patents can be developed after a reviewof the inventions herein. Prior art warning devices exist which warndrives of an oncoming jackknife, and which indicate fishtailing,principally relating to vehicles which do not employ a fifth wheel. Anumber of recognized prior art inventions recognized by their patentshave disclosed the positioning of a device, such as a block or abutmentmember, within guide lugs in the entranceway or V-slot of the slideplate of a fifth wheel mounted on the tractor to prevent jackknifing.However, these inventions have not been widely adopted. Representativeexamples include U.S. Pat. Nos. 2,553,959; 2,962,301; 3,972,542 and4,068,860. In the U.S. Patents to Dirks et al., this concept wasemployed and implemented by a generally horizontal longitudinallyextending restraining tongue rigidly mounted on the trailer undersideand terminating as a forward tapered tongue tip (or bracket) between thelugs in an extended station position. A remotely controlled cylinderattached to the tongue caused horizontal tongue reciptocation betweenthe retracted and forward extending position to prevent jackknifes.After a review of the detailed description below it will be appreciatedthat none of the prior art attempts accomplish the results of thepresent inventions as detailed in the description.

SUMMARY OF THE INVENTIONS

The present control system functions in accordance with the describedpreferred embodiments of the present inventions normally in a positionof actual or potential engagement with the fifth wheel and acts as ananti-jackknife control system and warning device which allows the driverto set the limits of swing of the trailer while driving in accordancewith road conditions and rig movement. The present system allows thedrive to set the control system by a control method implementing thefunctions of the apparatus. The control system provides for permissibleswings of the articulated vehicles about a full swing arc, about alimited controlled arc lesser than the full swing, and free within alimited arc lesser than the controlled arc under supervision of aposition control system. As such a jackknife is not permitted to occurwhen the control system is engaged, for system-fifth wheel engagementprevents rotation to the extent that a jackknife could occur. Instead,the system control the swing allowing the driver to continue to drivethe vehicle and in the event a sever limit is reached the system causesthe tractor to move into a controlled plow which averts the jackknifeaccident.

In accordance with the preferred embodiments of the inventions theapparatus is easily mounted on the trailer bed frame by bolting acontrol system frame to one of the horizontal trailer bed frame beammembers. This mounting locates a pivotal engaging bar limit elementwhich pivotally flips into and out of an engagement zone positionbetween the ears of a tractor's conventional fifth wheel the undercontrol of a switch accessible to the driver. The control system enablesthe position of the engaging bar limit element in the engagement zone tolimit the trailer to approximately 12 to 14 (nominally 15) degrees ofswing about a kin pin pivot point from the normal linear alignment ofthe tractor trailer, as well as swing through a wider controlled swingradius. Normally when the trailer turns it pivots completely around onthe fifth wheel. When the limit element of the anti-jackknife controlsystem is engaged, the hitch turns about 15 degrees in free swing beforethe fifth wheel contacts the engaging bar. At this point the trailer canproceed to swing an additional 10 to 15 degrees in the same direction upto an end limit (preferred to be at 26 degrees). At the start of theadditional swing an alarm sounds in the cab. This alarm tells the driverthat the trailer is swinging towards the limit of turn and warns himthat the transition point from permitted free swing is passed. At thispoint, the operator has the option of releasing the limit bar and byflipping a control switch inside the cab which releases the fifth wheelfor free rotation, allowing full pivoting action of the fifth wheel, orhe can leave the limit bar element in position and the limit bar elementwill continue to move sideways to the point of limit of lateral movementfixed by normal setting to a 10 to 14 degree additional swing limit thetractor trailer movement, or to another angular (lateral) limit set bythe driver. During this period of additional swing further lateralmovement of the limit member is slowed (unless stopped by the driver),and a potential jackknife can be controlled by the driver who has beenwarned to steer in the direction that the rear of the trailer issliding. If the tractor is sliding, the driver will steer in thedirection that the rear of the tractor is sliding.

When the limit element is in place, its fifth wheel control systeminteraction prevents further relative angular movement by the positionof the limit element in a laterally stopped position, so that the tiresof the tractor will plow sideways at an angle and the truck remainsunder control plowing down off of the tires like a plow. Tire plow willbring the rig to a halt, but the danger of turn over and jackknife hasbeen prevented.

In accordance with the invention, in operation the engaging bar limitelement is to be normally in position between the ears of the fifthwheel. After coupling of the kingpin in the center of the fifth wheelV-slot the driver engages the engaging bar and the control system andlimit element is engaged. The unit is adjustable to reasonable positionsfor speed, as it is in order to accomodate twisting mountain roads,(lower speeds permit a greater degree of swing without interialconditions causing a jackknife occurrence), between end limits ofmovement. These end limits of movement may be set by the driver beforeor after a time when the ears move the abutment limit element into thewarning zone. Mechanically the system is designed so the the limitsetting will be between an end limit of approximately 15 degrees to atotal limit of a preferred 26 degrees (30 is the maximum range). Freeswing between 12 and 16 degrees is permitted as being the the normalapproximate 15 degree swing in either direction permitted before theanti-jackknife warning control signal is made noticeable. In the engagedposition the unit feeds back to the driver the relative tractor positionwith the cab mounted control panel which contains the warning lights andaudio alarm system, which, even when trailer angle is not being limitedby throwing an auxiliary switch, serves as a safety feedback devicenotifying the driver that the trailer is moving toward its limits andapproaching a position where it could jackknife if the system was notemployed.

This warning condition would occur should the driver momentarily dozeand the truck becomes unstable, waking him and indicating correctiveaction when the engagement bar is in its normal active position. Thedriver can react to the warning. The bar can be disengaged by flippingthe control and/or limit switch on a control panel on or off. When it isnot needed and when the truck is under control, such as when the rig isgoing through city streets, pulling into filling stations and ontofreeway ramps or backing to a loading dock the control switch may beswitched off to disengage the bar control. Thus disengaged the controldevice allows the truck to negotiate such as easily as if the unit werenot in place.

In situations where when the engagement bar limit element is disengagedwhen the rig would reach an unstable condition, as when it went off ontothe berm, switching on the control system would cause the engagement barto move the limit element into position centered initially and then bepermitted to move to the limit set by the driver where it is held untilthe rig has traction.

The engaging bar of the control device in the present system iscontrolled by a panel control monitor, providing feedback to the driveras to the status of the engaging bar's position, whether it is engagedor not, and whether the relative movement is within or beyond normalfree range. This panel signals the driver to engage the system if it isnot but should be engaged. A fail-safe disengagement system is providedto prevent possibly dangerous feedback in the event of control failure.

The foregoing overview of the functions of the system is implemented ina system control apparatus which can be installed on new and existingtrailer vehicles. This control of a constantly moving rig is achieved byan apparatus which is composed of a few elements which are rugged andreliable, with minimal maintainence requirement and which are protectedfrom damage of impact or weather conditions. The system is implementedby elements whose interaction can best be understood by reference to theparticular elements of the structures described for the preferred andalternate embodiments of the inventions, which will be described indetail with reference to the accompanying drawings in which:

FIG. 1 is a view in elevation illustrating the locations of theanti-jackknifing control apparatus of system constucted in accordancewith the preferred embodiment of the present invention.

FIG. 2 is a schematic perspective view of the control apparatusillustrated in FIG. 1 looking downwardly from the trailer illustratingthe anti-jackknifing abutment engaging bar and limit element inengagement position between the ear portion of the fifth wheel's slideplate; and

FIG. 2A is a schematic perspective view of the control apparatus of FIG.1A looking downwardly from the trailer illustrating an alternateembodiment of the anti-jackknifing apparatus; and

FIG. 3 is a plan view looking upwardly beneath the fifth wheel(illustrated in phantom) of the anti-jackknifing control apparatus as itenters the engagement position.

FIG. 3A is a similar plan view looking upwardly beneath the fifth wheel(illustrated in phantom) of the alternate embodiment of FIG. 2A in theengagement position.

FIG. 4 is a sectional elevation taken on the line 4--4 in FIG. 3.

FIG. 4A is a sectional elevation taken on line 4--4 of FIG. 3A.

FIG. 5 is a schematic circuit diagram of electrical elements of thecontrol panel; and

FIG. 6 is a schematic fluid control diagram.

FIG. 7 is a schematic sectional view of the preferred engaging bar shafthousing taken along the line 4--4 in

FIG. 8 is a perspective view of a modified anti-jackknifing apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to the drawings in greater detail, the preferred embodimentof the invention is illustrated in FIGS. 1-7, while alternateembodiments are shown in FIGS. 2A, 3A, 4A and a modified embodimentillustrated in FIG. 8. All embodiments are carried on a tractor-trailerrig illustrated generally in FIG. 1.

A tractor 10 and a trailer 20 make up two intercoupled articulatedvehicles, what is often called a rig, a tractor trailer coupled througha fifth wheel slide plate 14 of the tractor. For the purpose ofillustration the tractor 10 of FIG. 1 has a cab 11 and a bed or platform12 having mounted thereon a conventional fifth wheel assembly 13, 14,15, including a disc shaped slide plate 14 pivotally secured at bothsides thereof by a fifth wheel journal mount 15 to brackets 13 which arefixedly secured to the platform or bed of the tractor 10.

The trailer 20 is coupled to the fifth wheel assembly by a kingpin 19which projects rigidly downwardly from the bolster baseplate 16underlying the mainframe or underframe 21 of the trailer 20, andgenerally crossing two or more cross frame beam members 22 of themainframe 21. As the tractor or truck 10 is backed beneath the trailer20 the bolsterplate 16 contacts the slanting slide plate surface of thefifth wheel and the kingpin 19 enters V-slot 17 (FIG. 2) of the slideplate 14. The V-slot of the preferred embodiments is a conventionalV-slot having therein a relatively straight longitudinal portion 17a anda diverging portion 17b forming the angular V-slot and defining the earportions 18.

As shown in FIG. 2 and FIG. 2A this V-slot 17 acts as a guide for thekingpin coupling. In the present inventions these V-slot ears act as afeedback mechanism input for the control of the articulation of thevehicles. This coupling of the tractor trailer is the conventionalinterconnection of the tractor with the trailer. The kingpin is usuallyclamped in the center of the disc slide plate 14 by a locking mechanism.There the kingpin is able to rotate about the vertical axis 19a of thekingpin as the trailer moves angularly relative to the tractor.

The control apparatus of the preferred embodiment of the inventions, asillustrated in FIGS. 1, 2, 7 and 2A is preferably mounted beneath thetrailer. A cross frame beam 22 is located above and crossing theposition of the V-slot 17 when the tractor is coupled to the trailer.Above this V-slot position a mounting bar 25 is positioned. Lugs orbolts 25' secure the mounting bar 25 to the crossframe beam 22 of thetrailer. In some trailers when mounting the control apparatus aftertrailer manufacture it is necessary to remove a cross frame member, orto cut out a section thereof. Sometime the bolster plate 16 extendsrearwardly of the kingpin a distance which exceeds the distance ofrearward ear extension of the slide plate 14, in which case the bolsterplate has to be partially removed or an aperture cut therein toaccommodate the control apparatus.

The anti-jackknife control apparatus comprises an anti-jackknifeapparatus mounted beneath the trailer and the system controls which areillustrated and described herein.

The present apparatus is easily mounted on the trailer bed frame bybolting a control system support frame 23 to one of the horizontaltrailer bed frame 21 beam members 22 to which the mounting bar 25 isattached. In the preferred embodiment the mounting bar 25 is a bar withprojecting studs which is welded to the frame with the studs projectingrearwardly, and the support frame is placed with the studs projectingthrough beveled apertures in the front portion of the support frame 23,where lugs 25' lock the support frame tightly on the mounting bar. In analternate embodiment shown in FIG. 2A the mounting bar 125 is part ofthe support frame which is bolted to the frame by bolts 125'.

In the preferred embodiments the support frame 23 is horizontally andlongitudinally mounted. Generally it may be considered substantiallyrectangular; however, as seen from the drawings the front engagement barbracing section is wider than the rear cylinder mounting section of thesupport frame. This frame portion has side members 24 which extendaround the control apparatus and protect it. The sides have rearportions 23a and outwardly flaring portions 23b as well as forwardlyaligned bracing portions 23c and a front mounting bar 25, 125.

The support frame when mounted within the protective bed frame 21 of thetrailer surrounds the control apparatus and protects it from above, fromthe side, and from below. The mounting bar section and side of the frameis wide enough that the slide bar won't accidently penetrate theprotecting frame as it is protected by the bolster plate and wide enoughto slide up on the plate itself. As will be understood, whendisconnected from fluid, the engagement bar 29 limit element member 28will be retracted protecting it and the fluid operated cylinder 26 fromdamage. The forward limit member 28 may have a bifrucated end portion127 or preferably the end of the piston rod 26 may be bifrucated topivotally connect to the abutment means limit element link 28.

In the preferred embodiment the movable members of the control apparatusare the engagement bar elements indicated generally at 29 with theirabutment limit element member 28 mounted thereon, is moveable into andout of engagement position between the ear portions of the V-slot 17 bythe extensible piston rod member 26' of the fluid actuation cylinder 26.It will be understood that the support frame when horizontally mountedunderneath the trailer bed locates the engagement bar elements 29 in aposition generally above the V-slot. The shaft 30 of the engagement barelements 29 is journaled in a pair of lateral support housings 36. Thelateral orientation of the engagement bar elements 29 in relation to thesupport frame and thus to the frame of the trailer and V-slot of thefifth wheel is determined such that the limit member 28 may be pivotallymoved by shaft 30 rotation caused by linear movement of said extensiblepiston rod member 26' connected thereto by abutment pivot connection 27down into position in the engagement zone within the V-slot. There theear portions of the slide plate 14 may contact the limit member 28.

In the preferred embodiments the rotatable shaft 30 is journaled so asto permit lateral (linear) movement in the shaft housing. Also in thepreferred embodiments of the invention rotatable shaft 30 includes abushing which is an integral casting with the link of the limit element28 (or element 28 may be welded thereon) so as to form a pivotalengaging bar limit element which pivotally rotates into and out of anengagement position between the ears of a tractor's conventional fifthwheel the under control of a master control switch 70 on control monitorpanel 68 accessible to the driver in the cab 11. The position of theengaging bar limit element 28 in the engagement zone normally limits thetrailer to 12 to 16 degrees (nominally 15) of free articulation or swingto either side about a kinpin pivot axis point 19a from the normallinear alignment of the tractor trailer before a warning beeper or horn65 sounds. The ultimate lateral linear movement of shaft 30 may be setso as to be stopped by an limit stop 133 set by lock nut 135 in FIG. 2A(or by nipple 33 in FIG. 2) so that the angular relative swing aboutaxis 19' from a line interconecting the front of the tractor and rear ofthe trailer will not be more than approximately 26 to 30 degrees ineither direction allowing for a normal 15 (or 12 or 16) degree swing,plus an additional preferred 10 or 14 degrees. Normally, when thetrailer turns it pivots completely around on the fifth wheel. When thelimit element of the anti-jackknife control system is engaged and thehitch turns "15" degrees the hitch ear portion 18 contacts the engagingbar limit element 28. At this point the ear 18 drives the abutment limitelement 28 linearly in the housing in the direction of its own traveland the trailer can proceed to swing an additional amount in the samedirection (up to the preferred limit of 26 degrees). But, shortly afterthe start of this additional lateral movement occurs, an alarm sounds inthe cab. This alarm 65, which may include a flashing light 64, tells thedriver that the trailer is swinging in engagement toward its 26 (up to30) degree limit.

At this point, the operator has the option of releasing the limit bar 28by flipping the control switch 70 inside the cab which releases thefifth wheel for rotation by causing retraction of the piston rod ofcylinder 26 allowing full pivoting action of the fifth wheel, or he canleave the limit bar element in position in the engagement zone of theV-slot 17 and the limit bar element will continue to slide laterally. Asit moves sideways the fluid in chamber 32 will cushion and retardfurther lateral swinging movement as the chamber bleed orifice 32' (a60/1000ths drilled line) will allow the further lateral swing. Thisprovides the driver an additional 10 degrees of swinging movement andtime to react to the signal. This also allows the element 28 to bereleased from engagement with the fifth wheel ear.

At any point the lateral movement of the abutment whether while beingdriven sideways by the ear or in the center position where the limitelement is normally initially placed, the point of actual limit oflateral movement may be placed, the point of actual limit of lateralmovement may be fixed by the driver. Further swing movement from the 15or 16 degree danger point of articulation of the tractor trailermovement which causes more lateral traverse of the shaft 30 in thehousing 36 may be adjustably set under control of the driver by throwingthe limit switch 71 in the cab. In function limit switch 71 causes acheck valve actuator (not shown) to close the dash pot chambercheckvalves 72 and 73 in the hydraulic system and limit expression offluid from the dash pot fluid pressure and compression chamber 32 ofhousing 36. This acts to freeze the lateral shaft movement to oneallowed solely by the centered position of the abutment limit element,or to another angular (lateral) limit where is is driven by the ear 18of the slide plate 14 as set under control of the driver at the time heactivates limit switch 71. When the dash pot is frozen only furthercompression of fluid between the shaft 30 and the check valves 72 and 73is possible. This provides little lateral movement.

During the period when the shaft is sliding laterally in the housing andcompressing the fluid, the audible horn or speaker 65 warns the driverto steer in the direction that the rear of the trailer is sliding. Ifthe tractor is sliding, the driver understanding the feel of the tractormovement and alerted by the signal will steer in the direction that therear of the tractor is sliding.

When the limit element is in place in the engagement zone in the V-slot17 of the slide plate 14 the engaging abutment of the engaging bar andthe ears 18 of the slide plate of the fifth wheel control systeminteraction. When the engaging bar is locked in the center position itprevents further relative angular movement greater than about 15 degreesby maintaining the fixed position of the limit element in a laterallystopped position, and the tires of the tractor will move at an angle andplow sideways as the Tire plow will bring the rig to a halt, but thedanger of turn over and jackknife has been prevented.

If the potential danger is due to a curve on mountanious terrain and nojackknife is probable driver judgment will control the limit by thesetting made when the driver throws switch 71.

The engaging bar limit element is retracted when the trailer isdisconnected or when the control switch 70 is thrown to the disconnectposition (up to the flasher pole in FIG. 5). The engaging bar isadvanced by rotation of the shaft and link element 28 into theengagement position in position with the abutment limit element 28 inposition between the ears of the fifth wheel by the action of thecylinder. When initially thrown the hydraulic system is powered tocauses the shaft 30 which carries link element 28 to be centered betweenthe housings 36. At this time the check valves 72 and 73 are open andequalized pressure exists in the dash pot fail-safe chambers 32, actingto center the shaft therebetween.

Because of the ability to allow a variable overrun of the normalabutment position by throwing the variable check valve switch 71 onlyafter the shaft has been moved sideways, the unit is adjustable toreasonable positions for speed, and to accomodate twisting mountainroads, (lower speeds permit a greater degree of swing without interialconditions causing a jackknife occurrence), between settable end limitsof movement. The ultimate limit of movement beyond the 15 degree warningmark are usually set to an end limit of 26 degrees. However, even thoughthe ear engages the abutment, throwing the check valve limit switch onand the control switch off allows retraction to allow free rotation.

Normally the system should be engaged to permit the warning system tofunction. This warning condition would occur should the drivermomentarily doze and the truck becomes unstable, waking him andindicating corrective action (which can include throwing the switch 71and steering in the direction indicated by the audio system).

When the driver is going over ice and snow, he can vary the limit of theamount of swing by turning on the extra limit switch 71 and hold theshaft at a specific point until he has traction and then may turn offthis fluid lock and allow free swing of the tractor trailer.

The engagement bar 29 bar can be disengaged by flipping the switch 70 onthe control panel in cab 11 when it is not needed and when the truck isunder control, such as when the rig is going through city streets,pulling into filling stations and onto freeway ramps or backing to aloading dock. In order to disengage the control engagement bar isrotated by cylinder 26 retraction (under spring 60 bias, or preferablyby air retraction bias caused when the control switch 70 is thrown, or acombination thereof) of the extensible member 26' rotating the link onwhich limit element 28 is fixed to allow the truck to negotiate such aseasily as if the unit were not in place.

When control switch 70 is thrown off, the switch is effectively moved upto the poles of the flasher signal light emitting diode 90 for thecontrol monitor panel as shown in FIG. 5. This flashing LED is flashedby a flasher control element 91, such as the flip-flop LED flasher chipof National Semiconductor LM3903. This warning light may be yellowwarning the driver to turn on the control system by throwing the switch70 down. Thus engaged the switch 70 will activate cylinder solenoidvalve system to move the engaging bar into position, as well as activategreen operating signal, LED 92, on the control monitor when the pistonof the cylinder causes the contact switch 63 to close.

In situations where when the engagement bar limit element is disengagedwhen the rig would reach an unstable condition, as when it went off ontothe berm, switching on the control system immediately causes theengagement bar to move the limit element into a centered positioninitially and then moved to the limit set by switch 71 where it is helduntil you have traction. Most of the time the driver will throw bothswitches at the same time. Accordingly, they are located together on thepanel 68.

The engagement bar 29,30 has a shaft section which is journaled inhousing 36. In the mode of the preferred embodiment of the inventionillustrated by FIG. 4 a sealing ring 52 at each housing end is providedto position a O-Ring gasket 51 at the end and yet allow some fluid spaceto be maintained at the end of the chamber 32. Another O-ring gasket isprovided on the shaft adjacent the bushing 36. A grease fitting isprovided to allow introduction of grease so that the shaft can slide inhousing 36 on a grease film, as shown in FIG. 4.

In the best mode of the preferred embodiment the amount of fluid in thisdamping chamber may be fixed by closure of the normally open solenoidactuated dash pot check valve 73 and bleed control check valve 72 shownin FIG. 6 by switch 71. This switch locks fluid in the chamber 32 andallows no movement therefrom thus limiting with a fluid the furthersliding movement of the shaft 30 toward the limit end 37 of housing 36.In the preferred embodiment the bolt 133 is replaced by the end of thehydraulic coupling 33 threaded into the housing 36.

Normally the fluid used for control is air. The tractor is provided witha compressor and air reserve tank which maintains a pressure adequate tooperate any air brakes and the control system.

As shown in FIG. 6, the hydraulic system comprises a number of fluidconnection lines running from a reserve surge tank 75. Should there bean electrical failure or a drop of pressure in the main air reservenormally closed failure switch 66 opens causing a series of shutdownactions. A fail-safe check valve 74 closes, along with the othernormally open check valve 72. This traps fluid in the system dash pots32 at enough pressure to allow for fail-safe staged control shutdown.The surge tank 75 can be used like the dash pots 32, in which case thisis considered a fluid chamber which causes retraction of the cylinderwhen the check valve 74 is closed. In this alternative not shown, thecheck valve 74 would be located above the reservoir 75, and both valves72 and preferably 73 would close.

When check valve 74 closes it drops engaging bar operation pressure byopening the cylinder advance two way control valve 76 to exhaust 77 aswell as coupling cylinder retraction two way control valve 78 topressure. Normally these are in the engagement position shown in FIG. 6due to the action of solenoid 67. However on shutdown, these valvesbeing spring biased by the spring bias of solenoid 67, these valves moveto the fail-safe mode, causing the remaining pressure in dash pots 32 tobe used to retract the piston. Such a reaction will turn off the greenoperating light as the piston retracts and disconnects switch 63.

Many of the features of the alternate preferred embodiment are common tothe preferred embodiment and the alternate preferred embodiment, as wellas the modified embodiment. These features have generally been given thesame number and will not be separately discussed in redundant detail,however, some common important features will be discussed.

The trailer is normally supplied with fluid to drive cylinder 36 by airlines 53 which pass through a distribution valve box 54 (some lines willpass to the brake system) and from there to the anti-jackknifing controlsystem carried by support frame 23. From the box 54 the line (or lines)are distributed to the cylinder and other fluid devices by lines 55. Thecylinder and dash pot control valves are preferably housed in a fluiddistribution control box 56 from which they pass via fluid lines 58 (notshown in FIGS. 2A, 3A) to their controlled chambers (32 and 63) as shownin FIG. 6.

In the alternate embodiment the dash pot pressure centering control isnot used, but springs 32a bias the limit element 28 to a centeredposition. These springs have not been employed in the preferredembodiment, but, while redundant, they might be added. Similarly, in thealternate and modified embodiment, a spring 60 biases the piston 62 tothe retracted position, as does first embodiment's auxilary spring 60assist the preferred use of fluid pressure.

In the alternate embodiment shown in FIGS. 2A and 3A adjustment meansfor setting the limit of end of lateral travel of the shaft 30 areprovided by threaded bolt 133 having a head 34 and lock nut 35. Thetraverse shaft member 30 carries a ball 31 mounted within housing 36which has a bracket for securement to the threaded member 38. The member38 serves to mount the adjustable threaded bolt 133 on the frame.

In all embodiments the rear of the cylinder is pivotally mounted on theframe 23 by a vertically pivotal connector 40. In the preferredembodiments this connector has a semi-universal connection 40 whichallows the cylinder to move laterally as well as vertically, along withthe lateral movement of the abutment link 28. The abutment is movablealong with the cylinder as illustrated by the broken lines in FIG. 3 soas to prove support for the abutment in positions which are laterallyadjustable to vary the angular relationship between the tractor andtrailer.

FIG. 7 is a modified section of the shaft housing 36 showing one half ofthe engaging bar shaft 30 and engaging bar limit member 28 in accodancewith the best mode of this bar limit member 28 in accodance with thebest mode of this feature as illustrated like a section taken along line4--4 of FIG. 3. In this embodiment the wall of the engaging bar shafthousing 36 has inserted in the bore thereof a bushing 140 into which theshaft 30 is journaled for rotational and sliding movement. A snap ring141 maintains the bushing in place. The shaft is not required to fitwith a fluid seal to the sides of the bushing 140, and a small clearanceis provided to ease movement and minimize maintainence. The position ofthe shaft is controlled by the position of the piston 142 (one in eachof the dash pot fail safe chambers 32 located at either end of theshaft) which is provided with two O-rings 143 providing a fluid seal fordash pot 32. When the shaft contacts the piston 142 a contact switch(not shown here) pole is closed activating a warning signal. At theouter end of the dash pot fail safe chamber 32 is an O-ring 144 sealedend plug 145 held in place by a snap ring 146, as shown, or by athreaded adjustment nipple (not shown). The plug is provided with athreaded fitting aperature 146, and bleed aperature 147 having a fittingreceptacle 148. As will be understood, the end of the shaft 30 is shownabutting the piston 142. However, the bushing is approximately 3.5 in.long, and the shaft may slide freely to the left so that its illustratedend is away from the piston 142 by a distance of about 1.34 in. beforeits other end contracts the piston (not shown) in the housing at theother end. Thereafter, if the engaging bar 28 is driven by the ear ofthe fifth wheel engagment it will move the piston and compress the fluidin the dash pot fail safe chamber 32, expressing fluid through the bleedaperature 148 and/or the aperature 146 until it reaches the end plug.This distance of travel is approximately 2 and 3/16 in. less the amountof the spacing of the end plug, a distance which will maintain the endof the shaft within the bushing at the other end of the shaft housingdue to the axial dimensions of the piston and end plug.

It will be understood that the axis of the shaft is aligned to liewithin 2-3 inches of and parallel to the mounting bar which places theapparatus against the beam of the trailer's frame. This close mountingplaces the shaft directly above the center of the V-slot, and providesmaximum leverage for the engaging bar which itself is about 2 incheswide when it is moved into the V-slot engagement zone. It will beunderstood that the use of the bushing, piston and end plug allow (aswell as any adjustment nipple if needed, allow an installer to vary theextent of lateral slide of the shaft to a specific amount, and therebyto permit the free swing of the vehicles to be limited to 12-16 degrees(the amount of slide of the shaft before it reaches the piston) and thecontrolled arc to be limited to the amount of the limited free swing arcplus an additional 10-14 degrees (the controlled arc is determined bythe amount of piston slide) simply by replacing one or more of thesethree elements with others that have different axial dimensions. Thefluid pressure system is used to stop the axial movement of the pistonand control its position (and thus the controlled arc) as in the abovedescribed system.

When the fluid pressure in dash pot 32 is such as to hold the piston tothe left, as it is when the engagement bar is engaged and during itsmovement into the V-slot, the piston causes the limit member 28 to becentered in a neutral position between the ends of its permissibletravel. Because in the embodiment shown in FIG. 7 allows some free play,the member's movement in the vertical direction may cause engagementwith the side of the V-slot, but this will only cause the shaft to slideslightly to permit the member to be fully positioned. The bar membercentering may be aided by springs as shown in FIG. 3A.

If the limit member is engaged at a loading dock in a position in whichthe bar member 28 comes down outside of the V-slot, due to a sharparticulation turn of the vehicle, when the tractor moves forward theslide plate will either lift the limit member up above it until itslides above the V-slot (as it will with most of the V-slot slide platesused on tractors today) or cause the shaft to contact the piston andsound a warning signal to the driver.

FIG. 8 illustrated a modified embodiment of the invention which does nothave the laterally movable and preferred features of the inventionsillustrated by FIGS. 2 and 2A. In this embodiment, the abutment element128 is aligned vertically in relation to the longitudinal position ofthe frame and is carried by a slide 50 which is pivotally connected asat 51 to the forward end of the extensible piston rod member 26. Theslide in this modified embodiment is provided with anti-friction means53 to assure ease of movement within a V-shaped groove 52 which iscomplementary to the V-shaped grooved sides 53 of the slide. Thisarrangement assures solid lateral support for the abutment 126 whichprojects downwardly from the slide 50, but does not allow lateralmovement. The controls in such a system are along the lines of FIGS. 1-7however the lateral movement controls are eliminated and the abutmentmember is moved into place only when needed to control the lateralmovement of the abutment link 28 are eliminated. Instead, the switch 71closes check valve 73' like valves 72 and 73 to lock fluid in the rearof the chamber 63. In this embodiment the jackknifing movement will urgethe abutment element 128 rearwardly upon contact with the ears. Thismovement is retarded by the forward pressure in the rear of the cylinder36. Rearward movement is retarded and stopped by the switch 71 whichchecks further compression of the cylinder fluid. This arrangementallows some lateral movement, but the systems described in the preferredembodiment provides greater flexibility of control.

The various valves illustrated in the drawings to explain the functionof the hydraulic control may be combined into multi-function valveslocated in the distribution box 56. Similarly, the electrical controlsmay be altered by those skilled in the art to perform the describedfunctions by different elements; however, the preferred describedelements provide the control capability with simple, reliable andeffective means. As shown in FIG. 6, the dash pot 32 can bealternatively supplied with hydraulic fluid 160 through supply means161, to lock hydraulic fluid in the dash pot in leiu of air normallyused in the rest of the fluid system.

Indeed, after review of the foregoing detailed disclosure of thepreferred embodiments, as well as the alternate and modified embodiment,those skilled in the art will appreciate that further changes includingmodifications, rearrangements and alterations described elements may bemade, both now and in the future, without departing from the spirit andscope of the following claims.

What is claimed is:
 1. An anti-jackknifing apparatus for use inconnection with a coupling between a tractor having a fifth wheel with acoupling plate member having a longitudinal slot having a tapereddiverging opening defining two spaced ear portions extending rearwardlycarried on said fifth wheel of the tractor, and a trailer having aforward frame portion and a connector pin adapted for coupling to saidfifth wheel, said apparatus comprising:a support frame; said supportframe having a transverse forward frame mounting bar secured adjacent aforward end of said support frame for securement to said forward frameportion on said trailer in superposed relation to said slot and tothereby position the apparatus when mounted on said trailer against saidforward frame portion and under the trailer in such a position as tolocate the forward position of abutment means carried by said supportframe; position control means including abutment means having anabutment stop member, a fluid operated cylinder, lateral support meansare adjustable limit means carried by said support frame, said fluidoperated cylinder having an extensible member extending forwardly fromone end thereof; means for securing said fluid operated cylinder withinsaid support frame; said abutment means being coupled to said cylinderfor movement of said abutment stop member between a first positionextending into an engagement zone between the spaced ear portions ofsaid slot and a second position wherein movement of said extensibleelement moves the said abutment stop member out of said engagement zone;and said lateral support member means being carried within said supportframe having a fixed relation thereto and providing lateral support forsaid abutment means when in said first position where said abutment stopmember of said abutment means is normally positioned to arrest relativeangular jackknifing movement of said tractor and trailer whilepermitting limited relative angular back and forth swinging movementtherebetween about said connector pin coupling to said fifth wheel whenin said first position extending into said engagement zone; saidabutment stop member being mounted for contacting one of the earportions of said slot of said fifth wheel upon swinging movement and tobe driven by said one ear portion and moved from an initialear-slot-stop member engagement position to another ear-slot-stop memberengagement position displaced in the engagement zone plane defined bythe ear portions of said fifth wheel where further movement of saidtractor and trailer about said connector pin coupling in the directionof swinging is prevented, said adjustable limit means carried by saidposition control means for allowing a swinging movement after initialear-slot-stop member initial contact up to a limit of movement of saidabutment stop member where further relative angular swinging movement ofsaid tractor and trailer about said coupling in a swinging direction isprevented by said abutment stop member and said adjustable limit means,and allowing a reverse relative angular swinging movement up to a limitdetermined by said adjustable limit means.
 2. The structure set forth inclaim 1 including means for said fluid operated cylinder for moving saidabutment stop member from said first position to said second positionshould fluid pressure fail.
 3. The structure set forth in claim 1including a switch means for activation when said abutment stop memberis moved when in said first position to a predetermined position byengagement with one of said ear portions of said fifth wheel, and analarm means is provided for energization in response to activation ofsaid switch means.
 4. The structure set forth in claim 1 wherein saidabutment means when in said first position is carried in a position inwhich said abutment stop member is normally positioned in said slotbetween said ear portions, and wherein centering means is provided formoving said abutment stop member into a neutral centered position in theslot of the fifth wheel during the course of movement of said abutmentstop member into said first position.
 5. The structure set forth inclaim 1 wherein said abutment means is carried by said lateral supportmeans on a transversely movable shaft member journaled in a lateralsupport means housing of said support means carried by said supportframe for lateral sliding movement within said housing, and said lateralsupport means and said adjustable limit means act to limit said lateralsliding movement of said shaft member to a desired limit of free slidingmovement to thereby fix the amount or permissible angular swing or saidtrailer relative to said tractor.
 6. The structure according to claim 5wherein said lateral support means carries said abutment means andallows said abutment means to pivot upwardly to said second position anddownwardly to said first position in a vertical place between saidsecond and first positions.
 7. The structure set forth in claim 1wherein abutment means when in said first position is carried in saidslot between said ear portions and said support means includes alongitudinal guide within said longitudinal frame carrying said abutmentmeans.
 8. The structure set forth in claim 7 wherein said longitudinalguide includes a pair of opposed V-shaped guides and a slide thereincarrying said abutment means.
 9. Anti-jackknifing apparatus according toclaim 1 wherein said lateral support means includes a lateral supporthousing and a laterally movable shaft member journaled in said lateralsupport housing for lateral movement therein, and a fluid chamber insaid support housing into and against which said shaft moves when saidshaft moves laterally, and wherein said shaft may rotate after saidshaft has moved laterally a distance to move out of abutment with saidfifth wheel.
 10. Anti-jackknifing apparatus according to claim 9 whereinsaid shaft housing means includes adjustable lateral limit means to fixa desired lateral limit of free sliding movement of said shaft tothereby fix the amount of permissible angular swing of said trailerrelative to said tractor by stopping the lateral movement of the shaftand the abutment limit element and thereby arresting further angulartrailer movement when the limit element is unable to move further in thelateral direction due to the then stationary adjustable lateral limitmeans and slot of said fifth wheel.
 11. Anti-jackknifing apparatusaccording to claim 1 wherein said lateral support means includes alateral support housing and a laterally movable shaft member journaledin said lateral support housing for lateral movement therein, and afluid chamber in said support housing into and against which said shaftmoves when said shaft moves laterally, and wherein said shaft may rotateafter said shaft has moved laterally a distance to move out of abutmentwith said fifth wheel.
 12. An anti-jackknifing apparatus for use inconnection with a tractor trailer coupling wherein said tractor carriesa fifth wheel for coupling to a trailer mounted coupling pin to permitthe tractor to pull said trailer and wherein said apparatus comprises:afluid operated cylinder mounted on a base support member mounted on saidtrailer, said cylinder having an extensible member having a driven outerend extending forwardly from one end thereof; cylinder mounting means onsaid base support member for permitting pivotal movement in a verticalplane as well as lateral movement in a lateral plane on said basesupport member; abutment means coupled to the said driven outer end ofsaid extensible member having an abutment stop member having one endadapted for movement into and out of an engagement zone between spacedears of a longitudinal slot in said fifth wheel, which abutment means iscarried on a transversely extending shaft member journaled in supportmeans so as to permit lateral sliding movement of said abutment stopmember in a transverse direction as well as pivotal movement of saidabutment stop member upon shaft rotation; and said extensible memberhaving a pivotal connection at the drive end thereof with said abutmentmeans whereby linear movement of said extensible member from saidcylinder causes the rotation of said shaft and movement of an abutmentend of said abutment stop member into and out of said engagement zone.13. The structure set forth in claim 12 including adjustable limit meansin said support means for arresting movement of opposed ends of saidshaft member as it slides laterally in said support means. 14.Anti-jackknifing apparatus according to claim 12 wherein said supportmeans includes a lateral support housing and a laterally movable shaftmember journaled in said lateral support housing for lateral movementtherein, and a fluid chamber in said support housing into and againstwhich said shaft moves when said shaft moves laterally, and wherein saidshaft may rotate after said shaft has moved laterally a distance to moveout of abutment with said fifth wheel.
 15. An anti-jackknifing apparatusfor use in connection with a coupling of a tractor and trailer, saidtractor having a fifth wheel with a longitudinal outwardly tapering slottherein and said trailer having a frame thereunder, comprising:elongatedabutment means having a limit element pivotally movable in a verticalplane between a first position where it is adapted to extend whenmounted on said trailer into an intercept zone located within saidtapering slot and a second position retracted from and above said slot;a transverse shaft member journaled in shaft housing means supported bysaid frame beneath the trailer with said shaft member being transverselymovable within its journal mounting after engagement with said fifthwheel; said abutment limit element being mounted on said transverseshaft member; and a fluid operated actuation cylinder having extensiblemeans with pivotal connection to said abutment means at a point on saidabutment means remote from said transverse shaft member; said cylinderhaving reciprocal movement means coupled to said extensible means forpivoting said abutment element between said first and second positions.16. The structure set forth in claim 15 including means for pivotingsaid abutment limit element from said first to said second positionshould fluid pressure in said cylinder fail to cause retraction of saidabutment limit member from said intercept zone.
 17. The structure setforth in claim 16 wherein said means for pivoting includes spring meanscarried within said cylinder for closing said extensible means in theevent of fluid pressure failure.
 18. The structure set forth in claim 15including a switch adapted to be activated when said abutment limitelement is about in a position to avoid a jackknifing occurrence tocause operation of alarm means as a feedback of angular position of saidtrailer, and wherein said switch has a contact positioned a spaceddistance from an end limit of permissible lateral movement of saidtransverse shaft member in one direction in said shaft housing means soas to be contacted and activated by said shaft as said shaft moveslaterally toward said end limit to lateral movement of said shaft toprovide a feedback signal of the limit element's lateral position priorto a point when said limit element will stop lateral movement androtation of said trailer relative to said tractor.
 19. Anti-jackknifingapparatus according to claim 15 wherein said elongated abutment means,said transverse shaft member, said shaft housing means, and said fluidoperated actuation cylinder are surrounded, protected and carried bysupport frame means which is mounted on said trailer frame, andwhereinsaid cylinder and said abutment means are supported within saidsupport frame so as to avoid damage thereto when said abutment means isin said first position limiting the tractor and trailer against relativemovement to avoid jackknifing when said abutment means is extending intosaid engagement zone and when the abutment means is out of saidengagement zone.
 20. Anti-jackknifing apparatus according to claim 19wherein said limit means is adjustable and limits the extent of lateralmovement of said abutment means in said fluid chamber and saidadjustable limit means is adapted to stop further lateral movement ofsaid abutment means depending upon the setting of said adjustable limitmeans.
 21. Anti-jackknifing apparatus according to claim 15 wherein theamount of lateral movement of said transverse shaft member in said shafthousing means is limited by adjustable limit stop means. 22.Anti-jackknifing apparatus according to claim 15 wherein said shafthousing means includes a lateral support housing having a closed end anda laterally movable shaft member journaled in an open end of saidlateral support housing for lateral movement therein, and a fluidchamber in said support housing into and against which said shaft moveswhen said shaft moves laterally toward said closed end, and wherein saidshaft may rotate after said shaft has moved laterally a distance to moveout of abutment with said fifth wheel.
 23. Anti-jackknifing apparatusaccording to claim 15 wherein said abutment means is carried by saidtransverse shaft member and journaled in shaft housing means whichallows said abutment means to pivot upwardly and downwardly from asecond to a first position and centering means is provided to center theabutment means in a neutral position intermediate the limits of lateralshaft movement in said shaft housing means while said abutment means ismoving downwardly in the vertical plane.
 24. Anti-jackknifing apparatusaccording to claim 15 wherein the amount of lateral movement of saidtransverse shaft member in said shaft housing means is limited byadjustable limit means, andwherein said abutment means is carried bysaid transverse shaft member journaled in shaft housing means forallowing said abutment limit element to pivotally rotate upwardly anddownwardly from a second to a first position and centering means areprovided to center the abutment means in a neutral position intermediatethe limits of lateral shaft movement in said shaft housing means whilesaid abutment limit element is moving downwardly in the vertical plane.25. An anti-jackknifing apparatus for use in connection with a couplingbetween a tractor having a fifth wheel with a coupling member having alongitudinal slot having a tapered diverging opening defining two spacedear portions extending rearwardly carried thereon and a trailer having aforward frame portion, said apparatus comprising:support frame means;abutment means; and position control means coupled to said abutmentmeans, said support frame having mounting means for securing saidsupport frame to said trailer; said abutment means being carried by saidsupport frame and being coupled to said position control means formovement between a first position extending into an engagement zonewhich intersects a plane lying between the spaced ear portions of saidslot and a second position wherein the abutment means is retracted outof said engagement zone; and support means, carried by said supportframe having a fixed relation thereto, for providing support for saidabutment means when in said first position; said support means allowingdisplacement movement of said abutment means by driving engagement ofsaid ears of said fifth wheel slot and said abutment means from aninitial first position of said abutment means in said plane to adisplaced first position of said abutment means in said plane to permitadditional relative swinging movement of said tractor and trailer aftersaid driving engagement of said abutment means by said ears; and saidposition control means being drivingly coupled to said abutment meansfor moving said abutment means to said first position while allowingmovement of said abutment means in said first position, and to retractsaid abutment means to said second position, and limit means forlimiting movement of said abutment means while it is in said firstposition and after it has been engaged by one of said ears of said fifthwheel to arrest relative swinging movement between the tractor andtrailer.
 26. Anti-jackknifing apparatus according to claim 25, whereinsaid support means includes a lateral support housing having a fluidchamber into which a laterally movable member of said abutment means isjournaled for lateral movement; and wherein lateral movement of saidmember in said fluid chamber is limited by said limit means. 27.Anti-jackknifing apparatus according to claim 25 wherein said shaft mayrotate after said shaft has moved laterally a distance to move saidabutment means out of abutment with said fifth wheel. 28.Anti-jackknifing apparatus according to claim 25 wherein said limitmeans is adjustable to adjust the permissible movement of said abutmentmeans in said plane.
 29. Anti-jackknifing apparatus according to claim25 wherein said support frame includes a support mounting bar adapted tobe connected to said trailer and to position said abutment means insuperposed relation to said slot.
 30. Anti-jackknifing apparatusaccording to claim 25 wherein said support housing includes a lateralsupport housing having a closed end and said movable member is a shaftjournaled in an open end of said lateral support housing for lateralmovement therein, and there is provided a fluid chamber in said supporthousing against which said shaft moves when said shaft moves laterallytoward said closed end, and wherein said abutment means is coupled tosaid control means for rotation of said shaft after said shaft has movedlaterally a distance to move an abutment member of said abutment meansout of abutment with said fifth wheel.
 31. Anti-jackknifing apparatusaccording to claim 30 wherein there is provided a switch means activatedwhen said abutment means has been displaced by ear engagement from saidinitial first position to cause operation of alarm means as a feedbackof angular position of said trailer and permit activation of saidcontrol means to retract said abutment means from said first position.32. Anti-jackknifing apparatus according to claim 30 wherein there isprovided a switch activated by a contact closed when the shaft is aspaced distance from the limit of permissible lateral movement of saidtransverse shaft member in one direction in said shaft housing means soas to be activated by said shaft as said shaft moves laterally toward alimit to lateral movement of said shaft to provide a feedback signal ofthe limit element s lateral position prior to a point when said limitmeans will stop lateral movement and rotation of said trailer relativeto said tractor about the tractor trailer coupling.
 33. Ananti-jackknifing apparatus according to claim 15 wherein said positioncontrol means include centering means which causes said abutment meansto move to an initial neutral first position between the ears of saidfifth wheel as said abutment means is moved to said first initialneutral position by said position control means, andsaid abutment meansis coupled to said position control means to allow movement from saidinitial neutral position to another position by driving engagement withthe ears of said fifth wheel up to a limit position restricting swingingmovement about said coupling.
 34. Anti-jackknifing apparatus accordingto claim 33 wherein said support means includes bias means which allowssaid abutment means to pivot upwardly to said second position anddownwardly to said first position in a vertical plane and acts to biasthe abutment means to said neutral position while said abutment means ismoving in the vertical plane intermediate the limits of movement of saidabutment means from said initial first position to said limit position.35. Anti-jackknifing apparatus according to claim 33 wherein saidabutment means includes an abutment member which is adapted to extenddownwardly in said first position and a shaft connected to andsupporting said abutment member, said shaft being journaled for rotationin shaft housing means at both ends and being slideable in both lateraldirections in said shaft housing means, and said bias means biases saidshaft to a neutral position between ends of permissible lateral movementof said shaft in the shaft housing means.
 36. An anti-jackknifingapparatus for use in connection with a coupling between a tractor havinga fifth wheel with a coupling member having a longitudinal slot having atapered diverging opening defining two spaced ear portions extendingrearwardly carried thereon and a trailer having a forward frame portion,said apparatus comprising:support frame means; abutment means; andposition control means coupled to said abutment means, said supportframe having mounting means for securing said support frame to saidtrailer; said abutment means being carried by said support frame andbeing coupled to said position control means for movement between afirst position extending into an engagement zone which intersects aplane lying between the spaced ear portions of said slot and a secondposition wherein the abutment means is retracted out of said engagementzone; and support means, carried by said support frame having a fixedrelation thereof, for providing support for said abutment means when insaid first position; said support means allowing engagement of saidabutment means by said ears of said fifth wheel slot after said abutmentmeans is positioned in an initial neutral first position of saidabutment means in said plane; said position control means beingdrivingly coupled to said abutment means for moving said abutment meansto said first position while allowing limited swinging movement of saidtractor and trailer when said abutment means are in said first position,and to retract said abutment means to said second position, saidabutment means being coupled to said position control means for allowinglimited relative movement of said tractor and trailer in a swingingdirection after engagement of said abutment means by an ear of saidfifth wheel, and adjustable limit means for limiting movement of saidabutment means while said abutment means is in said first position aftersaid abutment means has been engaged by one of said ears of said fifthwheel; said adjustable limit means determining the degree of permissiblerelative swinging movement between the tractor and trailer. 37.Anti-jackknifing apparatus according to claim 36 wherein said abutmentmeans is carried by lateral support means on a tranversely movable shaftmember journaled in a lateral support means housing of said supportmeans carried by said support frame means so as to permit lateralsliding movement of said shaft member within said housing, and saidlateral support means includes said adjustable limit means to limit saidlateral sliding movement of said shaft member to a desired limit of freesliding movement to thereby fix the amount of permissible angular swingof said trailer relative to said tractor.
 38. An anti-jackknifingapparatus according to claim 36 wherein said position control meansincludes centering means which causes said abutment means to move tosaid initial neutral first position between the ears of said fifth wheelas said abutment means is moved to said first initial neutral positionby said position control means, andsaid abutment means is coupled tosaid position control means to allow movement from said initial neutralposition to another position by driving engagement with the ears of saidfifth wheel up to a limit position restricting swinging movement aboutsaid coupling.
 39. Anti-jackknifing apparatus according to claim 36wherein said support means includes bias means which allows saidabutment means to pivot upwardly to said second position and downwardlyto said first position in a vertical plane and acts to bias the abutmentmeans to said neutral position, while said abutment means is moving inthe vertical plane, intermediate the limits of movement of said abutmentmeans from said initial first position to said limit position. 40.Anti-jackknifing apparatus according to claim 36 wherein said abutmentmeans includes an abutment member which is adapted to extend downwardlyin said first position and a shaft connected to and supporting saidabutment member, said shaft being journaled for rotation in shafthousing means at both ends and being slideable in both lateraldirections in said shaft housing means, and said bias means biases saidshaft to a neutral position between ends of permissible lateral movementof said shaft in the shaft housing means.
 41. Anti-jackknifing apparatusaccording to claim 36 wherein said support means includes a lateralsupport housing having a fluid chamber into which a laterally movablemember of said abutment means is journaled for lateral movement; andwherein lateral movement of said member in said fluid chamber is limitedby said limit means.
 42. Anti-jackknifing apparatus according to claim36 wherein said shaft may rotate after said shaft has moved laterally adistance to move said abutment means out of abutment with said fifthwheel.
 43. Anti-jackknifing apparatus according to claim 36 wherein saidsupport frame includes a support counting bar adapted to be connected tosaid trailer and to position said abutment means in superposed relationto said slot.
 44. Anti-jackknifing apparatus according to claim 36wherein said support housing includes a lateral support housing having aclosed end and said movable member is a shaft journaled in an open endof said lateral support housing for lateral movement therein, and thereis provided a fluid chamber in said support housing against which saidshaft moves when said shaft moves laterally toward said closed end, andwherein said abutment means is coupled to said control means forrotation of said shaft after said shaft has moved laterally a distanceto move an abutment member of said abutment means out of abutment withsaid fifth wheel.
 45. Anti-jackknifing apparatus according to claim 36wherein there is provided a switch activated by a contact closed whenthe shaft is a spaced distance from the limit of permissible lateralmovement of said transverse shaft member in one direction in said shafthousing means so as to be activated by said shaft as said shaft moveslaterally toward a limit of lateral movement of said shaft to provide afeedback signal of the limit element s lateral position prior to a pointwhen said limit means will stop lateral movement and rotation of saidtrailer relative to said tractor about the tractor trailer coupling. 46.Anti-jackknifing apparatus according to claim 36 wherein there isprovided a switch means adapted to be activated when said abutment meanshas been displaced by ear engagement from said initial first position tocause operation of alarm means as a feedback of angular position of saidtrailer and permit activation of said control means to retract saidabutment means from said first position.
 47. An anti-jackknifingapparatus for use in connection with a coupling between a tractor havinga fifth wheel with a coupling member having a longitudinal slot having atapered diverging opening defining two spaced ear portions extendingrearwardly carried thereon and a trailer having a forward frame portion,said apparatus comprising:support frame means; abutment means; andposition control means coupled to said abutment means, said supportframe having mounting means for securing said support frame to saidtrailer; said abutment means being carried by said support frame andbeing coupled to said position control means for movement between afirst position extending into an engagement zone which intersects aplane lying between the spaced ear portions of said slot and a secondposition wherein the abutment means is retracted out of said engagementzone; and support means, carried by said support frame having a fixedrelation thereto, for providing support for said abutment means when insaid first position; said support means allowing engagement of saidabutment means by said ears of said fifth wheel slot after said abutmentmeans is positioned in an initial neutral first position of saidabutment means in said plane; said position control means beingdrivingly coupled to said abutment means for moving said abutment meansto said first position while allowing movement of said abutment means insaid first position, and to retract said abutment means to said secondposition, and wherein said position control means include centeringmeans for causing said abutment means to move to said initial neutralfirst position between the ears of said fifth wheel as said abutmentmeans is moved to said first initial neutral position by said positioncontrol means, and said abutment means is coupled to said positioncontrol means for allowing movement from said initial neutral positionto another position by driving engagement with the ears of said fifthwheel up to a limit position restricting swinging movement about saidcoupling, and wherein is included limit means for limiting relativeswinging movement of said tractor and trailer while said abutment meansis in said first position and after said abutment means has been engagedby one of said ears of said fifth wheel to arrest relative swingingmovement between the tractor and trailer.
 48. Anti-jackknifing apparatusaccording to claim 47 wherein said support means includes bias meanswhich allows said abutment means to pivot upwardly to said secondposition and downwardly to said first position in a vertical plane andacts to bias the abutment means to said neutral position while saidabutment means is moving in the vertical plane intermediate the limitsof movement of said abutment means from said initial first position tosaid limit position.
 49. Anti-jackknifing apparatus according to claim47 wherein said abutment means includes an abutment member which isadapted to extend downwardly in said first position and a shaftconnected to and supporting said abutment member, said shaft beingjournaled for rotation in shaft housing means at both ends and beingslideable in both lateral directions in said shaft housing means, andsaid bias means biases said shaft to a neutral position between ends ofpermissible lateral movement of said shaft in the shaft housing means.50. An anti-jackknifing apparatus for use in connection with a couplingof a tractor having a fifth wheel with a longitudinal outwardly taperingslot therein and a trailer having a frame thereunder,comprising:elongated abutment means having limit element pivotallymovable in a vertical plane for movement between a first position wheresaid limit element is adapted to extend when mounted on said trailerinto an intercept zone located beneath said abutment means to a firstposition located within said tapering slot and a second positionretracted from within said slot; a transverse shaft member mounting saidabutment for pivotal movement into and out of said intercept zonejournaled in shaft housing means supported by said frame beneath thetrailer; and actuation means coupled to said shaft member for movingsaid transverse shaft member to cause pivoting of said abutment elementbetween said first and second positions, and said limit element of saidabutment means when stopped in position arrests relative rotationalmovement of said tractor and trailer about said coupling.
 51. Ananti-jackknifing apparatus according to claim 50 wherein said shafthousing means includes a lateral support housing having a fluid chamberinto which said laterally movable shaft member is journaled for lateralmovement into and against which said shaft moves when said shaft moveslaterally, and wherein said shaft may rotate after said shaft has movedlaterally a distance to move out of abutment with said fifth wheel.